Reference wavelengths in the spectra of Fe, Ge, and Pt in the region near 1935 Å

Wavelengths of seven spectral lines of Fe I, Ge I, and Pt I between 1932 Å and 1938 Å have been measured with uncertainties of less than 1×10−4 Å (5 parts in 108) with Fourier-transform spectroscopy. These lines provide accurate standards for wavelength calibration of ArF excimer lasers operating at 193 nm. Previously reported wavelengths of Fe I, Cu II, and Ge I were evaluated for calibration of the absolute wavelength scale. Calibrations based on Fe I and Ge I were found to differ systematically by several parts in 108. A calibration based on Cu II was internally inconsistent at a level of 2 parts in 107 and was not used. Improved wavelengths for an additional 147 lines of Pt I and Pt II and 161 lines of Kr II in the region 1636 Å to 3151 Å are also reported.